Projects
Quantification of Surface Water Storage in Low Elevation Coastal Zones using SWOT: implications for Vertical Land Motion (SWOT-LECZ-VLM)
Principle Investigator: Makan Karegar (Institute of Geodesy and Geoinformation, University of Bonn)
Co-Investigator(s): Mohammad J. Tourian
The LECZ includes river deltas and coastal wetlands and is home to a significant portion of the world's population and important infrastructure such as ports, airports, and power plants. These areas are vulnerable to impacts of rapid changes in (i) sea and river water levels, (ii) land surface height, and (iii) terrain features. Factors contributing to changes in water height include high water levels associated with storms, tidal amplification, river discharge, and atmospheric forcings which can lead to property damage, displacement of communities, and economic losses. Changes in land surface height due to short-term Surface Water Storage (SWS) changes together with natural and anthropogenically driven long-term Vertical Land Motion (VLM) exacerbate the impact of rising sea level and river flooding. While sea-level rise is considered a universal coastal threat, the compounding effects of land height change are only beginning to be recognized. In recent years, long-term VLM in LECZs has been attracting considerable attention. In the downstream catchment where the LECZs and floodplains are located, surface water is often a major contributing factor to the Total Water Storage (TWS) changes. However, deformation at shorter timescales, often caused by SWS changes, remains poorly understood partly due to i) sparse conventional in-situ water and land height measurements and difficulty of accessing for managing and instrumenting low-lying coastal plains, ii) poor performance of hydrological models in LECZ and complexity and computational cost of hydrodynamical models, iii) the absence of a comprehensive and cross-disciplinary approach, which often hinders an integrated approach to these aspects. This knowledge gap is targeted within this project.
This project aims to quantify SWS variation in LECZs using the recently launched SWOT and complementary satellite missions, and to model short-term VLM in LECZs through GNSS CORS sites and the state-of-the-art SWS data. While the SWOT KaRIn provides revolutionary SWS observations, it faces challenges in LECZs, such as complex estuarine terrain, limited vegetation penetration, complex tropospheric conditions, and low topographic roughness. To harness the full potential of SWOT KaRIn, we will develop methodologies to combine SWOT data with ancillary information from complementary satellite missions, such as satellite imagery and satellite nadir altimetry. We will process, analyze, and model GNSS CORS data across various time scales to quantify VLM caused by short-lived storm events, floods, sub-seasonal and seasonal flows, and long-term changes. In particular, the project aims to improve the accuracy of GNSS VLM measurements on sub-daily and daily time scales during extreme weather conditions and/or ocean tidal loading, and to contribute to a deeper understanding of elastic deformation modeling in LECZs. We will also aim to identify shallow deformation patterns using continuous GNSS Interferometric Reflectometry (GNSS-IR) and analyze how these patterns relate to meteorological and SWS changes. Understanding VLM on short timescales can benefit land management and help assess the failure probability of levees under climatic extremes such as floods, droughts, and heavy rainfall.
Our focus areas are the LECZs of Germany and the Mississippi Delta where studies have documented anomalously high rates of change in water levels, land elevations, and coastal morphology. We have chosen these study areas for several reasons. Both the LECZs of Germany and the Mississippi Delta are coastal regions with complex interactions between land, ocean, and atmosphere. These complexities make it challenging for the SWOT satellite mission to accurately capture the dynamic nature of these coastal areas, especially in monitoring SWS. Abundant data in these regions including GNSS and river gauge networks will enable the validation of our results.